package com.bruce.tool.common.util.trace;

import com.bruce.tool.common.exception.BaseRuntimeException;
import com.bruce.tool.common.exception.ErrorCode;
import com.bruce.tool.common.util.LogUtils;
import lombok.AccessLevel;
import lombok.NoArgsConstructor;
import lombok.extern.slf4j.Slf4j;

/**
 * twitter的snowflake算法 -- java实现
 * 
 * @author beyond
 * @date 2016/11/26
 */
@Slf4j
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class SnowFlake {

    /**
     * 起始的时间戳
     */
    private static final long START_STMP = 1535448652631L;

    /**序列号占用的位数**/
    private static final long SEQUENCE_BIT = 12;
    /**机器标识占用的位数**/
    private static final long MACHINE_BIT = 5;
    /**数据中心占用的位数**/
    private static final long DATACENTER_BIT = 5;

    /**
     * 每一部分的最大值
     */
    private static final long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
    private static final long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private static final long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

    /**
     * 每一部分向左的位移
     */
    private static final long MACHINE_LEFT = SEQUENCE_BIT;
    private static final long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private static final long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

    /**数据中心**/
    private long datacenterId;
    /**机器标识**/
    private long machineId;
    /**序列号**/
    private long sequence = 0L;
    /**上一次时间戳**/
    private long lastStmp = -1L;

    public SnowFlake(long datacenterId, long machineId) {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }

    /**
     * 产生下一个ID
     *
     * @return
     */
    public synchronized long nextId() {
        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new BaseRuntimeException(ErrorCode.SYSTEM_ERROR.getCode(),"Clock moved backwards.  Refusing to generate id");
        }

        if (currStmp == lastStmp) {
            //相同毫秒内，序列号自增
            sequence = (sequence + 1) & MAX_SEQUENCE;
            //同一毫秒的序列数已经达到最大
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            //不同毫秒内，序列号置为0
            sequence = 0L;
        }

        lastStmp = currStmp;
        //时间戳部分
        //数据中心部分
        //机器标识部分
        //序列号部分
        return (currStmp - START_STMP) << TIMESTMP_LEFT
                | datacenterId << DATACENTER_LEFT
                | machineId << MACHINE_LEFT
                | sequence;
    }

    private long getNextMill() {
        long mill = getNewstmp();
        while (mill <= lastStmp) {
            mill = getNewstmp();
        }
        return mill;
    }

    private long getNewstmp() {
        return System.currentTimeMillis();
    }

    public static void main(String[] args) {
        for (int i = 0; i < (1 << 12); i++) {
            new Thread(() -> LogUtils.info(log,TraceNoUtils.fetchTraceNo())).start();
        }
    }
}